Is sealed, cooked chicken only good to the advertised 'best before date until you open it?

I have a package of Pinty's Oven Roasted Chicken Strips and it says "Best Before Nov 17 09". If I open the package, and place the chicken in individual zip loc bags, will this shorten their lifespan? I.e. will they only be good until the advertised best before date if I leave them in their original packaging?|||i think as long as you put them back in the cooler quickly they shouldnt have a shorter life.|||They will keep longer than the "best by" date if you put them in the freezer instead of the fridge.|||if you freeze the individual ziploc bags they can keep or else use before Nov 17,09!